Filter assembly with filtrate flow control and control components

ABSTRACT

Disc filter assembly in which a plurality of filter discs are mounted on common shaft for rotation to selectively dispose disc surfaces under vacuum in a confined body of slurry through a portion of said rotation and to discharge formed cake from said surfaces by &#39;&#39;&#39;&#39;blow&#39;&#39;&#39;&#39; action through another portion of rotation. Each disc has plurality of sectors in sequential arrangement circumferentially of shaft mounted on a hollow center shaft fabricated from standard industrial components, inclusive of steel pipe forming shaft exterior and plurality of tubular members of oblong section in welded circumferentially spaced arrangement interiorly of pipe providing a conductive passage in communicating relation to at least one sector for applying vacuum and blow thereto under control of filter valve.

United States Patent Peterson et al.

[54] FILTER ASSEMBLY WITH FILTRATE FLOW CONTROL AND CONTROL COMPONENTS[72] Inventors: C. Lynn Peterson; Clarence John Peterson,

both of Salt Lake City, Utah [73] Assignee: Peterson Filters &Engineering Company,

Salt Lake City, Utah [22] Filed: Oct. 6, 1969 [21] Appl. No.: 863,947

[ 51 May 2, 1972 FOREIGN PATENTS OR APPLICATIONS 1,009,952 11/1965 GreatBritain ..2l0/331 Primary ExaminerFrank A. Spear, .Ir. Attorney-McGrewand Edwards [57] ABSTRACT Disc filter assembly in which a plurality offilter discs are mounted on common shaft for rotation to selectivelydispose disc surfaces under vacuum in a confined body of slurry througha portion of said rotation and to discharge formed cake from saidsurfaces by blow action through another portion of rotation. Each dischas plurality of sectors in sequential arrangement circumferentially ofshaft mounted on a hollow center shaft fabricated from standardindustrial com ponents, inclusive of steel pipe forming shaft exteriorand plurality of tubular members of oblong section in weldedcircumferentially spaced arrangement interiorly of pipe providing aconductive passage in communicating relation to at least one sector forapplying vacuum and blow thereto under control of filter valve.

12 Claims, 14 Drawing Figures Patented May 2, 1972 3,659,716

3 Sheets-Sheet 1 INVEN'IORS a. L YN/V PETERSON B Y 0L 4 RE/VCE pnmso/v ATTORNEYS Patented May 2, 1972 3,659,716

3 Sheets-Sheet 2 EtEZZI N I III IIIIIIII' I III FIG. 4

7; FIE. 6

INVILTJ'I'URS C. LY/V/V PETERSON BY CLARENCE l. PETERSON 6//%SKM f ATTOR/VE Y5 Patented May 2, 1972 3,659,716

3 SheetsShe t 5 IN VENTURS 0. LY/V/V PETERSON BY CLARENCE J. PETERSOVFIG. I2

A 7' TOHNE Y5 FILTER ASSEMBLY WITH FILTRATE FLOW CONTROL AND CONTROLCOMPONENTS This invention relates to disc filter construction and moreparticularly relates to the center shaft assembly of such a filter. Theinvention also relates to a novel type of connector defining a passagebetween a sector bell and a conduit in the shaft, and to a novel type ofvalve and associated transition casting for use with either disc or drumfilters.

The provision of an economical design of center shaft for rotary vacuumdisc filters has been a continuing problem of the industry. In the past,it has been common practice to provide cast sections with ports cast in.The sections are joined in the final assembly and considerable machiningof components is required before assembly. The cast shaft stands wearwell due to the heavy wall thickness of the cast in ports, but due tothe ever increasing price of cast iron, such a shaft is now becominguneconomical, particularly for small size filters.

Another difficulty has been experienced with fabricated shafts usingcircular tubes as conduits, in that the relatively thin wall tends toerode rapidly under the blast or downwardly directed nozzle efiect ofthe filtrate and air-flow immediately under the sector where the sectorbell connects to the shaft. In vacuum filter design, an effort is madeto maintain velocities in the various drainage channels that will permitthe air flow to sweep out residual filtrate. If the velocities are toolow, there is a tendency for residual filtrate to be retained in thedrainage channels. Then when the reverse pressure of blow" comes on todischarge the cake, this residual filtrate is driven back into the cakeand defeats the purpose of the filter which is to dewater the cake tothe lowest possible filtrate or moisture content.

The present invention represents a significant departure from prior artpractices in the construction and assembly of a hollow center shaft forvacuum disc filters. One of the innovations is the utilization ofcomponents of preformed shapes and dimensions which are available on themarket and may be used in the assembly with only a minor amount ofmachining required to provide an efficient and durable assembly ofreduced cost and shipping weight and incorporating improved hydraulicsin directing fluid flow in and out of said shaft.

Another innovation of our invention is the provision of a novel type ofconnector for joining a sector bell passage with an interior passage ofthe shaft. This connector is a casting having a radius turn to thelengthwise axis of the interior passage, and preferably the passage inthe castings has an increasing cross-section as it approaches theinterior passage or is curved to prevent direction outflow, therebylessening the blast effect of fiow into said interior passage. Byturning and expanding the flow, any erosion that results will occurwithin the connector which is easily replaced at low cost compared withinterior tube replacement. Such casting also is suited for use as areplacement part in filters now having a right angle turn connection.

Still another innovation of this invention is to utilize outside weldingprocedure in the assembly. The exterior component of the assembly may becommercial pipe, such as steel pipe, plastic pipe or similarly shapedcommercial tubing such as oil well casing tubes. The interior conduitscomprise metallic or plastic pipe or tubing, preferably of oblong orrectangular section. When the exterior component is to be joined to aninterior tubular member, alined openings are provided as by torchcutting, if metallic, so as to provide a relatively narrow gap betweenthe oblong tube and the outer shaft which can receive an arc or gas weldfrom above, or when plastic components are used and similar openings areformed, the connection is made by heat welding from above.

Yet another innovation is the provision of a novel valve assembly inwhich pressure or blow connection of a bulk head type is adapted to goon either side of the valve chamber eliminating the need for right andleft hand units. A transition casting is provided for association withthe valve to reduce velocities and prevent erosion and blast out in thevalve head. This valve and associated transition casting are suitablefor use as drum filter components.

Accordingly, it is an object of our invention to provide a novel centershaft assembly for disc filters which is inexpensive, durable, resistantto erosion and lightweight and incorporates improved hydraulics in thecontrolled flow of fluid in and out of said shaft.

Another object of this invention is the provision of a simple,economical and efficient center shaft construction for disc filterassemblies which is formed from commercially available components andrequires a minimum of special castings and machining in the assembly.

A further object of the invention is to provide novel flow control meansand connections in a disc filter having a novel center shaftconstruction.

Still another object of our invention is to provide a novel combinationof control valve and transition casting which is well adapted for use onboth disc and drum filters.

Other objects reside in novel details of construction and novelcombinations and arrangements of parts, all of which will be set forthin the course of the following description.

The practice of our invention will be described with reference to theaccompanying drawings illustrating a typical center shaft constructionand other structural assemblies utilizing novel features of ourinvention, and which may be produced in a variety of materials. In thedrawings, in the several views of which like parts bear similarreference numerals,

FIG. 1 is a partially broken side elevation view of a center shaftassembly according to our invention with broken areas shown in sectionto illustrate the shaping and arrangement of interior parts;

FIG. 2 is a sectional view taken along the line 2-2, FIG. 1, andappearing essentially as an end elevation of one filter sector supportedby and connected to the center shaft shown in FIG. 1;

FIG. 3 is an end elevation view of one valve head shown in the FIG. 1assembly;

FIG. 4 is a fragmentary partially broken end elevation view similar toFIG. 2 and drawn to an enlarged scale, showing details of the centershaft construction and sector mounting thereon in section;

FIG. 5 is a fragmentary section taken along the line 5-5, FIG. 4, andshowing an arrangement for use of abrasion-resistant inserts in thebottom of the interior tubes of the shaft;

FIG. 6 is a fragmentary partially broken side elevation view similar toFIG. 4 and drawn to the scale of FIG. 4, showing cutting and weldingdetails and the flow control of the casting utilized as the connectorbetween a sector bell and an interior tube of the center shaft assembly;

FIG. 6A is a partially broken vertical section similar to FIG. 6 andshowing a modified form of connector for directing blast discharge awayfrom a direct flow onto the walls of an interior tube with which it isconnected;

FIG. 7 is a side elevation view, partially in section of a transitioncasting and its connection with a valve head for reducing erosioneffects to which the valve head is subjected;

FIG. 8 is an end elevation or plan view of the wear plate portarrangement included in the transition assembly shown in FIG. 7;

FIG. 9 is an end elevation of the valve head end of the center shaftassembly as shown in FIG. 1 and drawn to a reduced scale to illustrate alefthand connection to an associated vacuum receiver;

FIG. 10 is an end elevation similar to FIG. 9 and illustrating a tripleconnection with a vacuum receiver which may be provided;

FIG. 11 is another end elevation similar to FIG. 9 and illustrating arighthand connection to the vacuum receiver;

FIG. 12 is a vertical fragmentary section of a valve and associatedtransition casting mounted on a rotary drum and illustrating theincreasing cross section passage arrangement of such an installation;and

FIG. 13 is an end elevation of the valve shown in FIG. 12 illustrating atriple connection with a vacuum receiver by dash line representation.

The shaft assembly illustrated in FIG. 1 comprises an exterior component15 which as shown is an elongated hollow body such as tubing, pipe orthe like, preferably having its intermediate section 15a flanged at itsends for connection to flanged transition castings l6 and 16a which inturn are connected with valve heads at both ends as shown, or at leastone end. When all the filter components are assembled, the center shaftwill be horizontally disposed and suitably supported for rotation with aplurality of filter discs carried by the shaft being immersed in aslurry tank during a part of each revolution of the shaft and suitabledischarge mechanism, such as scrapers, will remove formed cake from thedisc surfaces through another portion of the revolution.

The tank, discharge mechanism, and shaft mounting are not features ofthe present invention and have not been illustrated in detail. Thesector assembly and fastening may be of any suitable type and as shownin FIG. 2 embody features of Ser. No. 651,344, filed June 19, 1967, forDisc Filter Sector Assembly and Separable Components Thereof, now U.S.Pat. No. 3,485,376 of Dec. 23, 1969. Bearings 18 and 19 support oppositeends of the shaft and bearing 18 is a part of a drive assembly for theshaft including gearing 20. Other supporting structure 21 is shown.While a plurality of discs will be supported lengthwise of the shaft,each comprising a plurality of sectors 22 in sequential arrangementcircumferentially of the shaft, only one such sector has been shown inFIGS. 1 and 2 with another fragment of a sector bell 22x also shown inFIG. 1, and additional illustration is considered unnecessary.

The shaft assembly includes a plurality of conduit members 23 incircumferentialiy spaced arrangement interiorly of the exteriorcomponent 15 of the shaft, each such conduit member being in conductivecommunication with a sector bell 22x and ports 24 and 25 of a pair ofvalve heads 26 and 27 mounted on opposite ends of the shaft. Usually theconduit members 23 are other than round, preferably being of oblong orrectangular section, and may be available commercial tubing having thedesired shape and dimension including round. In the assembly illustratedin FIG. 1, the intermediate section 15a of the outer component comprisesa major part of the total length of the shaft and will carry all of thediscs and sectors of the assembly.

A convenient arrangement for interior conduit and exterior sectorsupport has been provided and is illustrated in FIG. 1, which isrepresentative of a lO-disc filter with double ended valve assembly andmetallic shaft components. A novel type of turn flow casting 17 has beenutilized which turns the flow towards the associated valve and in theIO-disc arrangement five of said castings are directed toward valve 27and the other five are directed toward valve 26 at the drive end. Thesecastings permit torch cutting rectangular openings 28 through the wallof intermediate section 15a where each supported sector is to be mountedand an exterior welded connection is made between section 15a, theconduit members 23 and the turn flow castings 17 as best shown in FIGS.4, and 6.

Castings 17 not only prevent direct blast effect but also provide aconnecting passage 170 with a radius turn to the lengthwise axis of theconnected conduit member 23 which turns and expands the flow so that anyerosion of consequence takes place within the casting. The castings areeasily replaced when they eventually become worn. A great deal of theturbulence of the right angle turn of conventional connections isavoided and a reduction in pressure drop is obtained. When therectangular openings 28 are cut in intermediate section a, the sectionmodulus is reduced by about 50 percent but this is replaced with oblongor rectangular components that have a relatively high section modulusdue to their shape.

In addition to their utilization as components of the novel shaftassembly shown in FIG. 1, the castings 17 may be installed in prior artcast iron shafts of previously installed equipment which is stilloperational to prevent erosion of the right angle connection previouslyprovided, and better hydraulics also are attained because of suchmodification. As shown in FIG. 6, castings 17 have a depending portion17x which projects downwardly into the welded opening and therebyprovides protection for the welded seams against the scouring action ofthe flow.

A modified form of transflow casting has been shown in FIG. 6A. Thiscasting 57 has a connecting passage 57a extending from an upper recessportion to a bottom discharge outlet defined by a flanged dependingportion 57x. Passage 57a is curved sufficiently so that the top openingof said passage is within the vertical plane of the lower curved wall572 and this curved portion provides protection against blast effectfrom the associated sector passing directly onto a wall of theassociated interior conduit member 23 with which it is connected, as allflow in direct descent impinges on the curved surface 57z and isdirected forwardly into the conduit members 23 due to the change indirection.

When the flow approaches the valve heads 26 and 27, the velocity isreduced by the transition casting 16 or 16a which provides a passage ofincreasing cross section in the direction of the valve. The expansion ofthe flow reduces its velocity and greatly diminishes the erosion andblast out in the valve head. Other features of the construction andfunctioning of the valves 26 and 27 not shown in detail in FIG. 1 havebeen illustrated in other views of the drawings and will be describedhereinafter.

It will be apparent from the illustration of the hollow center shaftconstruction shown in FIG. 1 and the preceding description relatingthereto that such an assembly substantially eliminates the need forspecial patterns, as the main shaft components, particularly those shownin intermediate section 15a comprise an outer component which may beformed of tubing or pipe and preferably is cylindrical. The wallthickness of said member only requires that it provide sufficientstrength to support the interior components and the number of discsmounted on its exterior surface which are required for a given assembly.The interior passages are formed by tubular components and are supportedfrom the exterior component usually by welding.

The shaping of the exterior component and the inner tubular membersparticularly in cross section may be selected to meet both strength anddurability requirements, as well as providing improved hydraulics in theflow of the fluid in and out of the shaft. Where the dimensionalrequirements permit the use of available industrial materials, as, forexample, steel or plastic pipe for use as the outer component, it isonly necessary in a given assembly to cut the pipe sections to thedesired length, secure flanges on the ends where flanges are nototherwise provided and then cut the tubular members for the interiorassembly to the desired length. Such members preferably are other thanround in section and for best effects rectangular or oblong sections areutilized. Such members may be formed from relatively thin materialparticularly when an insert member is provided to protect the bottomsurface from blast effect from the associated filter sector.

Openings 28 are formed in the wall of the exterior component as by torchcutting when metal tubing or pipe is used or forming similar openings inplastic pipe, after which the turnflow castings are fitted in theopenings so formed in the exterior component and also in the tubularconduits and the components are connected as by electric are or gaswelding for metallic assemblies and heat welding for plastic assemblies.Consequently, the only patterns required are for the tum-flow castingsl7 and the transition castings 16 and 16a adjoining the valves 26 and27, and only a minimum of machining is required to complete a givenshaft. The shaft when so assembled is greatly reduced in weight withoutsacrificing durability and the principal wear occurs on component partswhich are easily replaced at low cost when necessary.

A novel feature of the valve assembly 27 shown in FIGS. 1 and 3 is theprovision of a blow connection which is on the vertical center line asviewed in FIG. 3. Frequently, in plant layout, it will be advantageousto have the vacuum receiver on only one side of the filter. The blowconnection 128 shown in FIG. 3 is a bulkhead type, i.e., it isfabricated rather than cast into the valve head 27 and can go to eitherside of the valve chamber 27, depending on the hand of the valve whichis required. Such arrangement is not only advantageous in the layout bybeing able to locate the receiver 29 on either side of the filter asshown in FIGS. 9 and 11, but in addition a triple connection can beprovided as shown at 30 in FIG. 10. In the latter arrangement, a veryhigh volume of air flow will be handled by the double connection to thedrying zone of the filter. Thus, only one pattern is required for bothleft and righthand valve heads. Openings 33 in valve head 27 which arenot connected are closed by a suitable plug 33a (FIG. 1).

A preferred arrangement for assembly of the tubular conduits 23interiorly of the outer component a and the use of the connectors ortum-flow castings 17 for conducting flow from and into the sector bells22x will now be described with reference to FIGS. 4, 5 and 6. As shownin FIG. 4, the outer component 15a of the shaft has flanged end portions30, each having a series of circumferentially spaced openings a forinterconnection with similar flanged portions 16x on the transitioncastings l6 and 16a as by bolting. A suitable number of openings 28 areformed circumferentially of outer component 15a in rows spacedlengthwise of said component to seat the required number of sectors 22forming each disc and the required number of discs. By using rectangulartubing for conduits 23, a relatively narrow gap 31 is establishedbetween opening 28 and conduit 23 which can receive an arc weld 32without too much bleedout or additional welding. Also, to further reduceerosion of conduits from blast effect, abrasionresistant strips 34 maybe fitted against the bottom wall 23a of the tubular conduits 23.

Also as shown in FIG. 6, casting 17 is made to permit depending portion17x to project downwardly into the opening 28 and thereby providesprotection for the welded seams against the scouring action of the flow.Casting 17 may be held in place and sealed against outer component 15aby a rectangular gasket 35 and tightened by the half nuts 36:: on theradial rods 37 cooperating with nuts 36.

Valves 26 and 27 shown in FIGS. 1, 3, 7 and 8 are structural andfunctional equivalents and have been given different reference numeralsto designate their left and righthand positions as viewed in FIG. 1.Valve 27, for example, has a cone surface 27m of about 45 and valve 26is similarly shaped. The openings 33 are formed on this conical surface(FIG. 3) and the snout connections 33x are of relatively short length,giving a good functional appearance and effect. The spring 38 (FIGS. 1and 7) is used to exert pressure on the valve head until it is seatedand then the vacuum holds the valve faces tightly together. The stem orthreaded bolt 39 turns with the shaft. The spring is stationary againstthe valve head and a thrust bearing (not shown) lets the stem rotateagainst the stationary spring.

FIG. 8 shows a wear plate 27p of the type used in an assembly such asshown in FIG. 7 wherein said wear plate is fitted onto the flanged endof transition casting 16a and has a series of elongated radial ports 40in circumferentially spaced arrangement which aline with the passages16m in the transition casting and although causing some restriction ofthe passage direct the expanding flow into another expanding passage 27nwithin valve 27 as indicated by the expanding arrow pattern in FIG. 7.This arrangement reduces incoming flow velocity and prevents erosion andblast-out in the valve head.

As mentioned in the earlier description, a combination of a valve, suchas valve 27, and a transition casting, such as 16a, are well suited forcontrolling pressure flow in a drum filter installation in the mannerillustrated in FIGS. 12 and 13. The drum filter is shown at 42 as havinga central trunnion 43 supported for rotation in a bearing assembly 44with piping connections 45 extending from its peripheral filteringsurface 48 to the inlet end of a transition casting 46, the opposite endof which connects to a valve 47. Except for minor dimensionaldifferences, casting 46 is the same as casting 16a and valve 47 is thesame as valve 27 previously described.

FIG. 13 illustrates valve 47 as having a triple connection with a vacuumreceiver (not shown) which is similar to the arrangement shown in FIG.I0. Such an arrangement permits location of the receiver on whicheverside of the filter best suits the requirements of the plant layout. Thepassage arrangement of casting 46 and valve 47 effectively reduces flowvelocity and prevents erosion within the valve head.

We claim:

1. In a disc filter assembly in which a plurality of filter discs aremounted on a common shaft for rotation therewith to selectively disposedisc surfaces under vacuum influence in a confined body of slurrythrough a portion of said rotation and to discharge formed cake fromsaid surfaces by pressure change on said surfaces through anotherportion of said rotation, each said disc comprising a plurality ofsectors in sequential arrangement circumferentially of the shaft, andvalve means associated with said shaft for selectively applying vacuumand pressure to each sector during each revolution of the shaft, theimprovement which comprises a hollow center shaft fabricated frompre-formed industrial components, inclusive of a hollow tubular bodyforming the exterior component of the shaft and a plurality of tubularmembers disposed in circumferentially spaced relation interiorly of theexterior component, each said tubular member providing a conductivepassage in communication with at least one sector for applying vacuumand pressure thereto under control of a filter valve, and said tubularmembers welded to said exterior component for providing a structuralassembly to support the discs and transmit torque thereto duringrotation of said shaft.

2. A disc filter assembly as defined in claim 1, in which the tubularbody is steel pipe.

3. A disc filter assembly as defined in claim 1, in which the tubularbody is plastic pipe.

4. A disc filter assembly as defined in claim 1, in which the weldedconnections between the tubular members and the exterior component aredisposed below surface openings of said exterior component.

5. A disc filter assembly as defined in claim 1, in which connectingmeans are disposed between a tubular member in the shaft assembly and anassociated sector, said connecting means having a connecting passagewith a radius turn to the lengthwise axis of said member.

6. A disc filter assembly as defined in claim 1, in which the connectingpassage is of increasing volume approaching the tubular member.

7. A disc filter assembly as defined in claim I, in which the connectingpassage is of increasing cross section approaching the tubular member.

8. A disc filter assembly as defined in claim 1, in which connectingmeans are disposed between a conduit of oblong section in the shaft andan associated sector, said connecting means having a connecting passageat an oblique angle to the lengthwise axis of said conduit.

9. In a disc filter assembly in which a plurality of filter discs aremounted on a common shaft for rotation therewith to selectively disposedisc surfaces under vacuum influence in a confined body of slurrythrough a portion of said rotation and to discharge fonned cake fromsaid surfaces by pressure change on said surfaces through anotherportion of said rotation, each said disc comprising a plurality ofsectors in sequential arrangement circumferentially of the shaft, andvalve means associated with said shaft for selectively applying vacuumand pressure to each sector during each revolution of the shaft, theimprovement which comprises a hollow center shaft inclusive of metaltube forming the exterior component of the shaft and a plurality ofmetallic tubular members of a section other than round disposed incircumferentially spaced relation interiorly of the outer tube and witha small gap between adjoining surfaces of the tubular members and thetube, each said tubular member providing a conductive passage incommunication with at least one sector for applying vacuum and pressurethereto under control of a filter valve, and said tubular members weldedto said metal tube at the gap for support by said tube during rotationof said shaft.

10. A disc filter assembly as defined in claim 9, in which the tubularmembers are of oblong section.

11. In a filter assembly having a hollow body including at least onefilter medium surface and mounted on a shaft for rotation therewith toselectively dispose the filter medium surface under vacuum influence ina confined body of slurry through a portion of said rotation and todischarge formed cake from the filter medium surface by pressure: changeon said surface through another portion of said rotation, and valve.means associated with said shaft for selectively applying vacuum andpressure to the filter medium surface during each revolution of theshaft, the improvement which comprises a hollow center shaft having aplurality of tubular members disposed in circumferentially spacedrelation interiorly of the shaft, each said tubular member providing aconductive passage in communication with a filtrate conduit disposedbetween the filter medium surface and said shaft for applying vacuum andpressure to said surface under control of a filter valve, and said valvehaving a valve head with a blow connection that extends from a verticalcenter line on the exterior surface of the valve head to either side ofsaid center line in the internal chamber enclosed by said valve head.

12. in a filter assembly having a hollow body including at least onefilter medium surface and mounted on a shaft for rotation therewith toselectively dispose the filter medium sur face under vacuum influence ina confined body of slurry through a portion of said rotation and todischarge formed cake from the filter medium surface by pressure changeon said surface through another portion of said rotation, and valvemeans associated with said shaft for selectively applying vacuum andpressure to the filter medium surface during each revolution of theshaft, the improvement which comprises a hollow center shaft having aplurality of tubular members disposed in circumferentially spacedrelation interiorly of the shaft, each said tubular member providing aconductive passage in communication with a filtrate conduit disposedbetween the filter medium surface and said shaft for applying vacuum andpressure to said surface under control of a filter valve, inclusive of aplurality of circumferentially spaced port openings for selectiveconnection of at least two openings with a vacuum receiver on a selectedside of a vertical center line, and means for closing the openings notso connected.

l I. 1F i i

1. In a disc filter assembly in which a plurality of filter discs aremounted on a common shaft for rotation therewith to selectively disposedisc surfaces under vacuum influence in a confined body of slurrythrough a portion of said rotation and to discharge formed cake fromsaid surfaces by pressure change on said surfaces through anotherportion of said rotation, each said disc comprising a plurality ofsectors in sequential arrangement circumferentially of the shaft, andvalve means associated with said shaft for selectively applying vacuumand pressure to each sector during each revolution of the shaft, theimprovEment which comprises a hollow center shaft fabricated frompre-formed industrial components, inclusive of a hollow tubular bodyforming the exterior component of the shaft and a plurality of tubularmembers disposed in circumferentially spaced relation interiorly of theexterior component, each said tubular member providing a conductivepassage in communication with at least one sector for applying vacuumand pressure thereto under control of a filter valve, and said tubularmembers welded to said exterior component for providing a structuralassembly to support the discs and transmit torque thereto duringrotation of said shaft.
 2. A disc filter assembly as defined in claim 1,in which the tubular body is steel pipe.
 3. A disc filter assembly asdefined in claim 1, in which the tubular body is plastic pipe.
 4. A discfilter assembly as defined in claim 1, in which the welded connectionsbetween the tubular members and the exterior component are disposedbelow surface openings of said exterior component.
 5. A disc filterassembly as defined in claim 1, in which connecting means are disposedbetween a tubular member in the shaft assembly and an associated sector,said connecting means having a connecting passage with a radius turn tothe lengthwise axis of said member.
 6. A disc filter assembly as definedin claim 1, in which the connecting passage is of increasing volumeapproaching the tubular member.
 7. A disc filter assembly as defined inclaim 1, in which the connecting passage is of increasing cross sectionapproaching the tubular member.
 8. A disc filter assembly as defined inclaim 1, in which connecting means are disposed between a conduit ofoblong section in the shaft and an associated sector, said connectingmeans having a connecting passage at an oblique angle to the lengthwiseaxis of said conduit.
 9. In a disc filter assembly in which a pluralityof filter discs are mounted on a common shaft for rotation therewith toselectively dispose disc surfaces under vacuum influence in a confinedbody of slurry through a portion of said rotation and to dischargeformed cake from said surfaces by pressure change on said surfacesthrough another portion of said rotation, each said disc comprising aplurality of sectors in sequential arrangement circumferentially of theshaft, and valve means associated with said shaft for selectivelyapplying vacuum and pressure to each sector during each revolution ofthe shaft, the improvement which comprises a hollow center shaftinclusive of metal tube forming the exterior component of the shaft anda plurality of metallic tubular members of a section other than rounddisposed in circumferentially spaced relation interiorly of the outertube and with a small gap between adjoining surfaces of the tubularmembers and the tube, each said tubular member providing a conductivepassage in communication with at least one sector for applying vacuumand pressure thereto under control of a filter valve, and said tubularmembers welded to said metal tube at the gap for support by said tubeduring rotation of said shaft.
 10. A disc filter assembly as defined inclaim 9, in which the tubular members are of oblong section.
 11. In afilter assembly having a hollow body including at least one filtermedium surface and mounted on a shaft for rotation therewith toselectively dispose the filter medium surface under vacuum influence ina confined body of slurry through a portion of said rotation and todischarge formed cake from the filter medium surface by pressure changeon said surface through another portion of said rotation, and valvemeans associated with said shaft for selectively applying vacuum andpressure to the filter medium surface during each revolution of theshaft, the improvement which comprises a hollow center shaft having aplurality of tubular members disposed in circumferentially spacedrelation interiorly of the shaft, each said tubular member providing aconductive passage in communication with a filTrate conduit disposedbetween the filter medium surface and said shaft for applying vacuum andpressure to said surface under control of a filter valve, and said valvehaving a valve head with a blow connection that extends from a verticalcenter line on the exterior surface of the valve head to either side ofsaid center line in the internal chamber enclosed by said valve head.12. In a filter assembly having a hollow body including at least onefilter medium surface and mounted on a shaft for rotation therewith toselectively dispose the filter medium surface under vacuum influence ina confined body of slurry through a portion of said rotation and todischarge formed cake from the filter medium surface by pressure changeon said surface through another portion of said rotation, and valvemeans associated with said shaft for selectively applying vacuum andpressure to the filter medium surface during each revolution of theshaft, the improvement which comprises a hollow center shaft having aplurality of tubular members disposed in circumferentially spacedrelation interiorly of the shaft, each said tubular member providing aconductive passage in communication with a filtrate conduit disposedbetween the filter medium surface and said shaft for applying vacuum andpressure to said surface under control of a filter valve, inclusive of aplurality of circumferentially spaced port openings for selectiveconnection of at least two openings with a vacuum receiver on a selectedside of a vertical center line, and means for closing the openings notso connected.